In SporkHack, green dragon scale mail also gives the player a passive attack against monsters that damage the player: d6 poison damage, with the usual 5% instadeath chance accompanying it. (As usual with poison attacks, poison resistant monsters are immune to both the damage and the instadeath.)

In UnNetHack, this item is renamed poison dragon scale mail, and has a randomized appearance out of tatzelworm/amphitere/draken/lindworm/sarkany/sirrush/leviathan/wyvern/glowing dragon/guivre scale mail, matching the dragon species that has poisonous breath.

References

See Dragon scale mail for more detailed information on what makes dragon scale mail special and how to obtain it.